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  <div class="section" id="what-s-new-in-python">
<span id="whatsnew-index"></span><h1>What’s New in Python<a class="headerlink" href="#what-s-new-in-python" title="Permalink to this headline">¶</a></h1>
<p>The “What’s New in Python” series of essays takes tours through the most
important changes between major Python versions.  They are a “must read” for
anyone wishing to stay up-to-date after a new release.</p>
<div class="toctree-wrapper compound">
<ul>
<li class="toctree-l1"><a class="reference internal" href="3.6.html">What’s New In Python 3.6</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#summary-release-highlights">Summary – Release highlights</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#new-features">New Features</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#new-modules">New Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#improved-modules">Improved Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#optimizations">Optimizations</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#other-improvements">Other Improvements</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#deprecated">Deprecated</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#removed">Removed</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#porting-to-python-3-6">Porting to Python 3.6</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.6.html#notable-changes-in-python-3-6-2">Notable changes in Python 3.6.2</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="3.5.html">What’s New In Python 3.5</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#summary-release-highlights">Summary – Release highlights</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#new-features">New Features</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#new-modules">New Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#improved-modules">Improved Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#other-module-level-changes">Other module-level changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#optimizations">Optimizations</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#deprecated">Deprecated</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#removed">Removed</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.5.html#porting-to-python-3-5">Porting to Python 3.5</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="3.4.html">What’s New In Python 3.4</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#summary-release-highlights">Summary – Release Highlights</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#new-features">New Features</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#new-modules">New Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#improved-modules">Improved Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#cpython-implementation-changes">CPython Implementation Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#deprecated">Deprecated</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#removed">Removed</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#porting-to-python-3-4">Porting to Python 3.4</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.4.html#changed-in-3-4-3">Changed in 3.4.3</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="3.3.html">What’s New In Python 3.3</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#summary-release-highlights">Summary – Release highlights</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-405-virtual-environments">PEP 405: Virtual Environments</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-420-implicit-namespace-packages">PEP 420: Implicit Namespace Packages</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-3118-new-memoryview-implementation-and-buffer-protocol-documentation">PEP 3118: New memoryview implementation and buffer protocol documentation</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-393-flexible-string-representation">PEP 393: Flexible String Representation</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-397-python-launcher-for-windows">PEP 397: Python Launcher for Windows</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-3151-reworking-the-os-and-io-exception-hierarchy">PEP 3151: Reworking the OS and IO exception hierarchy</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-380-syntax-for-delegating-to-a-subgenerator">PEP 380: Syntax for Delegating to a Subgenerator</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-409-suppressing-exception-context">PEP 409: Suppressing exception context</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-414-explicit-unicode-literals">PEP 414: Explicit Unicode literals</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-3155-qualified-name-for-classes-and-functions">PEP 3155: Qualified name for classes and functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-412-key-sharing-dictionary">PEP 412: Key-Sharing Dictionary</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-362-function-signature-object">PEP 362: Function Signature Object</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#pep-421-adding-sys-implementation">PEP 421: Adding sys.implementation</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#using-importlib-as-the-implementation-of-import">Using importlib as the Implementation of Import</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#a-finer-grained-import-lock">A Finer-Grained Import Lock</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#builtin-functions-and-types">Builtin functions and types</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#new-modules">New Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#improved-modules">Improved Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#optimizations">Optimizations</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#deprecated">Deprecated</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.3.html#porting-to-python-3-3">Porting to Python 3.3</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="3.2.html">What’s New In Python 3.2</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-384-defining-a-stable-abi">PEP 384: Defining a Stable ABI</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-389-argparse-command-line-parsing-module">PEP 389: Argparse Command Line Parsing Module</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-391-dictionary-based-configuration-for-logging">PEP 391:  Dictionary Based Configuration for Logging</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-3148-the-concurrent-futures-module">PEP 3148:  The <code class="docutils literal"><span class="pre">concurrent.futures</span></code> module</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-3147-pyc-repository-directories">PEP 3147:  PYC Repository Directories</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-3149-abi-version-tagged-so-files">PEP 3149: ABI Version Tagged .so Files</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#pep-3333-python-web-server-gateway-interface-v1-0-1">PEP 3333: Python Web Server Gateway Interface v1.0.1</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#new-improved-and-deprecated-modules">New, Improved, and Deprecated Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#multi-threading">Multi-threading</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#optimizations">Optimizations</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#unicode">Unicode</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#codecs">Codecs</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#documentation">Documentation</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#idle">IDLE</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#code-repository">Code Repository</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.2.html#porting-to-python-3-2">Porting to Python 3.2</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="3.1.html">What’s New In Python 3.1</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#pep-372-ordered-dictionaries">PEP 372: Ordered Dictionaries</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#pep-378-format-specifier-for-thousands-separator">PEP 378: Format Specifier for Thousands Separator</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#new-improved-and-deprecated-modules">New, Improved, and Deprecated Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#optimizations">Optimizations</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#idle">IDLE</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.1.html#porting-to-python-3-1">Porting to Python 3.1</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="3.0.html">What’s New In Python 3.0</a><ul>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#common-stumbling-blocks">Common Stumbling Blocks</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#overview-of-syntax-changes">Overview Of Syntax Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#changes-already-present-in-python-2-6">Changes Already Present In Python 2.6</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#library-changes">Library Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#pep-3101-a-new-approach-to-string-formatting"><strong>PEP 3101</strong>: A New Approach To String Formatting</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#changes-to-exceptions">Changes To Exceptions</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#miscellaneous-other-changes">Miscellaneous Other Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#performance">Performance</a></li>
<li class="toctree-l2"><a class="reference internal" href="3.0.html#porting-to-python-3-0">Porting To Python 3.0</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="2.7.html">What’s New in Python 2.7</a><ul>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#the-future-for-python-2-x">The Future for Python 2.x</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#changes-to-the-handling-of-deprecation-warnings">Changes to the Handling of Deprecation Warnings</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#python-3-1-features">Python 3.1 Features</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#pep-372-adding-an-ordered-dictionary-to-collections">PEP 372: Adding an Ordered Dictionary to collections</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#pep-378-format-specifier-for-thousands-separator">PEP 378: Format Specifier for Thousands Separator</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#pep-389-the-argparse-module-for-parsing-command-lines">PEP 389: The argparse Module for Parsing Command Lines</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#pep-391-dictionary-based-configuration-for-logging">PEP 391: Dictionary-Based Configuration For Logging</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#pep-3106-dictionary-views">PEP 3106: Dictionary Views</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#pep-3137-the-memoryview-object">PEP 3137: The memoryview Object</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#new-and-improved-modules">New and Improved Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#other-changes-and-fixes">Other Changes and Fixes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#porting-to-python-2-7">Porting to Python 2.7</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#new-features-added-to-python-2-7-maintenance-releases">New Features Added to Python 2.7 Maintenance Releases</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.7.html#acknowledgements">Acknowledgements</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference internal" href="2.6.html">What’s New in Python 2.6</a><ul>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#python-3-0">Python 3.0</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#changes-to-the-development-process">Changes to the Development Process</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-343-the-with-statement">PEP 343: The ‘with’ statement</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-366-explicit-relative-imports-from-a-main-module">PEP 366: Explicit Relative Imports From a Main Module</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-370-per-user-site-packages-directory">PEP 370: Per-user <code class="docutils literal"><span class="pre">site-packages</span></code> Directory</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-371-the-multiprocessing-package">PEP 371: The <code class="docutils literal"><span class="pre">multiprocessing</span></code> Package</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3101-advanced-string-formatting">PEP 3101: Advanced String Formatting</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3105-print-as-a-function">PEP 3105: <code class="docutils literal"><span class="pre">print</span></code> As a Function</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3110-exception-handling-changes">PEP 3110: Exception-Handling Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3112-byte-literals">PEP 3112: Byte Literals</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3116-new-i-o-library">PEP 3116: New I/O Library</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3118-revised-buffer-protocol">PEP 3118: Revised Buffer Protocol</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3119-abstract-base-classes">PEP 3119: Abstract Base Classes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3127-integer-literal-support-and-syntax">PEP 3127: Integer Literal Support and Syntax</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3129-class-decorators">PEP 3129: Class Decorators</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#pep-3141-a-type-hierarchy-for-numbers">PEP 3141: A Type Hierarchy for Numbers</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#other-language-changes">Other Language Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#new-and-improved-modules">New and Improved Modules</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#deprecations-and-removals">Deprecations and Removals</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#build-and-c-api-changes">Build and C API Changes</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.6.html#porting-to-python-2-6">Porting to Python 2.6</a></li>
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<li class="toctree-l1"><a class="reference internal" href="2.5.html">What’s New in Python 2.5</a><ul>
<li class="toctree-l2"><a class="reference internal" href="2.5.html#pep-308-conditional-expressions">PEP 308: Conditional Expressions</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.5.html#pep-309-partial-function-application">PEP 309: Partial Function Application</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.5.html#pep-314-metadata-for-python-software-packages-v1-1">PEP 314: Metadata for Python Software Packages v1.1</a></li>
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<li class="toctree-l2"><a class="reference internal" href="2.5.html#pep-338-executing-modules-as-scripts">PEP 338: Executing Modules as Scripts</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.5.html#pep-341-unified-try-except-finally">PEP 341: Unified try/except/finally</a></li>
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<li class="toctree-l1"><a class="reference internal" href="2.4.html">What’s New in Python 2.4</a><ul>
<li class="toctree-l2"><a class="reference internal" href="2.4.html#pep-218-built-in-set-objects">PEP 218: Built-In Set Objects</a></li>
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<li class="toctree-l2"><a class="reference internal" href="2.4.html#pep-328-multi-line-imports">PEP 328: Multi-line Imports</a></li>
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<li class="toctree-l1"><a class="reference internal" href="2.3.html">What’s New in Python 2.3</a><ul>
<li class="toctree-l2"><a class="reference internal" href="2.3.html#pep-218-a-standard-set-datatype">PEP 218: A Standard Set Datatype</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.3.html#pep-255-simple-generators">PEP 255: Simple Generators</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.3.html#pep-263-source-code-encodings">PEP 263: Source Code Encodings</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.3.html#pep-273-importing-modules-from-zip-archives">PEP 273: Importing Modules from ZIP Archives</a></li>
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<li class="toctree-l2"><a class="reference internal" href="2.3.html#pep-293-codec-error-handling-callbacks">PEP 293: Codec Error Handling Callbacks</a></li>
<li class="toctree-l2"><a class="reference internal" href="2.3.html#pep-301-package-index-and-metadata-for-distutils">PEP 301: Package Index and Metadata for Distutils</a></li>
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<li class="toctree-l1"><a class="reference internal" href="2.0.html">What’s New in Python 2.0</a><ul>
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